He never mentioned doing a make-up day for the day missed. He only said it was raining. It did rain in the morning but cleared up by afternoon like most of the so cal storm systems moving through.
I give him a lot of extra projects like planting and clearing out planter areas etc… and pay his price quoted on the same day completed. These are outside his lawn care fee.
Side note: When I lived in LCV, the lawn care guys would be in ponchos shoving mowers in down-pours. Rain is part of the job, like cold and heat.